| 摘要 |
PURPOSE:To enable a tunnel drilling section at a facing to be indicated accurately and in a short time. CONSTITUTION:A TV camera 5 for photographing a facing 3, and a plurality of laser beam transmitters 6 emitting laser beams in parallel to the axial line of a tunnel, are arranged in the tunnel at the rear side of the facing 3. The image of the facing 3 photographed with the camera 5 is displayed on a monitor screen 8. Also, the drilling position of the facing 3 is displayed on the screen 8 on the basis of a positional relationship between an established tunnel drilling section and each laser beam luminous point, with reference to the facing irradiation points 10a to 10b of the laser beams photographed with the camera 5. |
